1. Field of the Invention
The present invention relates generally to self-sealing gaskets and, more particularly, to valve assemblies comprising gaskets including both an open aperture to provide a sliding seal and a split septum to provide a static seal.
The introduction of medical catheters to a patient generally requires passage of the catheter through the lumen of a previously introduced tube, sheath, guiding catheter, trocar sleeve, or the like. After initial introduction, it is frequently necessary to remove the catheter to perform some task (such as the injection of contrast medium) or to interchange the first catheter with a second. To facilitate such removal and/or interchange, a variety of "hemostatic valves" have been proposed to provide both a sliding seal against the introduced catheter (when it is in place) as well as a static seal (when the catheter has been removed). A typical hemostatic valve will include a gasket having both an open aperture for providing the sliding seal against the introduced catheter and a split septum for providing the static seal when the catheter has been removed.
While generally successful, conventional hemostatic valve designs suffer from certain drawbacks. Present designs often allow excessive blood loss, particularly during manipulation and repositioning of devices, such as guidewires, angioplasty catheters, atherectomy catheters, and the like. Blood loss can be a particular problem in newer "bare wire" atherectomy techniques where frequent repositioning of the device or wire are necessary. Many of the designs are rather complex and difficult to manufacture. Moreover, many of the present hemostatic valve designs are less effective when sealing against a vacuum, (e.g., during aspiration) than when sealing against positive blood pressure. Additionally, the gaskets within the hemostatic valve assemblies can become misaligned and damaged as a result of introducing a catheter therethrough. Such misalignment and damage are particular problems with catheters having rigid housings at their distal ends, such as atherectomy catheters having cutter housings at their distal ends. Such damage to the seal is often evident when leakage occurs through the static seal after the catheter has been removed.
For these reasons, it would be desirable to provide improved hemostatic valves for use with medical devices, such as guiding catheters, introducer sheaths, trocar sleeves, and the like. Such devices should provide an effective hemostatic seal at all times, including during the manipulation and repositioning of devices introduced therethrough. It would be further desirable if such housings and associated gaskets were easy to manufacture and use, and were able to seal against vacuum as well as against positive internal pressure. In particular, such improved hemostatic valves should include gaskets which readily receive a wide variety of catheters and which do not become misaligned and/or damaged as a result of catheter passage therethrough.
2. Description of the Background Art
U.S. Pat. No. 4,723,550, describes a hemostasis valve including an internal gasket having conical face and an axial passage. The passage may be radially constricted about a guide wire by axially compressing the gasket. U.S. Pat. No. 4,428,833, describes a molded, one-piece self-sealing gasket comprising a split-septum spaced-apart from a plug portion. U.S. Pat. No. 4,000,739, describes a hemostasis valve having disc-shaped gasket having a central aperture disposed against a disc-shaped split gasket. Other hemostatic valve structures are described in U.S. Pat. Nos. 4,960,412; 4,950,257; 4,752,287; and 4,436,519.